1、 One component RTV silicone rubber


The curing reaction of one component room temperature vulcanized silicone rubber is initiated by the moisture in the air. The commonly used crosslinking agent is methyltriacetoxysilane. Its Si-O-C bond is easy to be hydrolyzed. Acetyloxy groups and hydrogen groups in water form acetic acid, and the hydroxyl groups in water are moved to the original position of acetyloxy groups to become trihydroxymethylsilane. Trihydroxymethylsilane is very unstable, and it is easy to condense with linear organosilicon with hydroxyl end group to form cross chain structure. At ordinary times, the silicone rubber containing the silanol end group is packed into the sealed hose with various coordination agents such as filler, catalyst and crosslinking agent. When it is used, it is extruded from the container and vulcanized into the elastomer with the help of the moisture in the air, and the low molecular matter is released at the same time. Besides methyltriacetoxysilane, the crosslinking agent can also be silane containing alkoxy, oxime, amino, amido and ketone groups. When the alkoxy group is crosslinked with alkoxy group, the alcohol is released, which is called dealcoholized one component room temperature vulcanized silicone rubber. When the oxime group is crosslinked, oxime is generated, which is called dealcoholized room temperature vulcanized silicone rubber. Therefore, with the different crosslinking agents, single component room temperature vulcanized silicone rubber can be deacidified, dealcoholized, deamination, deamidation and dealkylation, etc., but deacidification is the most widely used type at present One used.








The curing time of one component room temperature vulcanized silicone rubber depends on the curing system, temperature, humidity and the thickness of silicone rubber layer. Under typical environmental conditions, after 15-30 minutes, the surface of silicone rubber can be non sticky, and the 0.3cm thick rubber layer can be cured in one day. The curing depth and strength will gradually increase in about three weeks.








One component RTV silicone rubber has excellent electrical properties, chemical inertness, heat resistance, natural aging resistance, flame resistance, moisture resistance, air permeability and other properties. They can keep elasticity for a long time in the range of - 60 ~ 200 ℃. It is not endothermic and exothermic during curing, and has small shrinkage after curing, and good adhesion to materials. Therefore, it is mainly used as adhesive and sealant, and other applications include in-situ forming gasket, protective coating and caulking material, etc. Many single-component silicone rubber adhesives exhibit automatic adhesion to many materials, such as most metals, glass, ceramics, and coagulation. For bare aluminum, for example, the shear strength can reach 200 LBF / inch2, and the tear strength can reach 20 LBF / inch2 (0.35 Joule / cm2). When the adhesion is difficult, the primer can be applied on the substrate to improve the bonding strength. The primer can be a reactive silane monomer or resin. When they solidify on the substrate, a modified surface suitable for silicone bonding will be formed.








Although the one component RTV silicone rubber is easy to use, because its vulcanization is based on the moisture in the lazy atmosphere, the thickness of the vulcanizate is limited, and it can only be used in the occasions requiring the thickness of less than 6 mm.








The curing reaction of one component RTV silicone rubber is gradually from the surface to the depth. The thicker the rubber layer, the slower the curing. When the deep part also needs rapid curing, the layered pouring and gradual curing method can be adopted, and some rubber materials can be added each time, and then added after curing, so as to reduce the total curing time. Adding magnesium oxide can accelerate the vulcanization of deep layer rubber.








Two component RTV silicone rubber two component RTV silicone rubber can be divided into condensation type and addition type.